Add various listener classes

Added various listener classes to support dispatch by message type
and request id.  The listeners are intended to form a pipeline:

	TopicSource =>
	MessageTypeDispatcher =>
	RequestIdDispatcher =>
	TypedMessageListener

Removed "PAP" from license.
Changed "handler" to "listener" in most places.
Simplified a test case.
Verified that no error message logged on success cases.
Removed println from test.
Updated some comments.

Change-Id: Ife265d14a6c5c8531601d9ce1343b88c1f8986a8
Issue-ID: POLICY-1444
Signed-off-by: Jim Hahn <jrh3@att.com>

1 files changed, 91 insertions, 0 deletions

diff --git a/policy-endpoints/src/main/java/org/onap/policy/common/endpoints/listeners/ScoListener.java b/policy-endpoints/src/main/java/org/onap/policy/common/endpoints/listeners/ScoListener.java
new file mode 100644
index 00000000..a3d33965
--- /dev/null
+++ b/policy-endpoints/src/main/java/org/onap/policy/common/endpoints/listeners/ScoListener.java
@@ -0,0 +1,91 @@
+/*
+ * ============LICENSE_START=======================================================
+ * ONAP
+ * ================================================================================
+ * Copyright (C) 2019 AT&T Intellectual Property. All rights reserved.
+ * ================================================================================
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.common.endpoints.listeners;
+
+import org.onap.policy.common.endpoints.event.comm.Topic.CommInfrastructure;
+import org.onap.policy.common.utils.coder.Coder;
+import org.onap.policy.common.utils.coder.CoderException;
+import org.onap.policy.common.utils.coder.StandardCoder;
+import org.onap.policy.common.utils.coder.StandardCoderObject;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Listens for receipt of a {@link StandardCoderObject}, translating it into an object of
+ * the appropriate type, and then passing it to the subclass.
+ *
+ * @param <T> type of message/POJO this handles
+ */
+public abstract class ScoListener<T> {
+
+    private static final Logger logger = LoggerFactory.getLogger(ScoListener.class);
+
+    /**
+     * Used to translate the standard object to an object of type "T".
+     */
+    private static final Coder coder = new StandardCoder();
+
+    /**
+     * Class of message this handles.
+     */
+    private final Class<T> clazz;
+
+    /**
+     * Constructs the object.
+     *
+     * @param clazz class of message this handles
+     */
+    public ScoListener(Class<T> clazz) {
+        this.clazz = clazz;
+    }
+
+    /**
+     * Receives an event, translates it into the desired type of object, and passes it to
+     * the subclass.
+     *
+     * @param infra infrastructure with which the message was received
+     * @param topic topic on which the message was received
+     * @param sco event that was received
+     */
+    public void onTopicEvent(CommInfrastructure infra, String topic, StandardCoderObject sco) {
+        // translate the event to the desired object type
+        final T msg;
+        try {
+            msg = coder.fromStandard(sco, clazz);
+
+        } catch (CoderException e) {
+            logger.warn("unable to decode {}: {}", clazz.getName(), sco, e);
+            return;
+        }
+
+        onTopicEvent(infra, topic, sco, msg);
+    }
+
+    /**
+     * Indicates that a message was received.
+     *
+     * @param infra infrastructure with which the message was received
+     * @param topic topic on which the message was received
+     * @param sco event that was received
+     * @param message message that was received
+     */
+    public abstract void onTopicEvent(CommInfrastructure infra, String topic, StandardCoderObject sco, T message);
+}